1. Field of the Invention
The present invention relates to a polyamide resin composition, and an article formed from the composition including a tank, tube, and the like. More particularly, it relates to a polyamide resin composition useful for the production of articles which have a lower tensile modulus as well as excellent oil resistance (especially, anti-gasoline fume permeability), thermal resistance, hydrolysis resistance, chemical resistance, moldability (especially, mold releasing property), impact resistance, etc., and to articles which are formed from the composition, the articles including gasoline tubes, hoses, packings, cams, gears, and the like.
2. Description of the Related Art
Recently, various multi-component resin compositions having a higher degree of impact resistance have been developed as a result of advanced research of polymer blends. In general, compositions comprising a polyamide resin, and an olefin polymer or a styrene polymer which is blended therewith are known as nylons. These nylons have a higher degree of impact resistance or a lower water-absorbing property, and include, for example, compositions of nylons and polypropylenes, compositions of nylons and ABS resins, compositions of nylons and polypropylene rubbers, and the like. However, because polyamide resins have a higher tensile modulus, articles having excellent flexibility cannot be obtained from these polyamide resin compositions.
In order to reduce the tensile modulus of the polyamide resin, polyamide elastomers, polyamide urethane copolymers, and the like have been prepared by block copolymerization of a polyamide (nylon 6, nylon 12, aromatic polyamides, etc.) as a hard segment and a polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), aliphatic polyester diol or the like as a soft segment. Although these resins have a lower tensile modulus, they provide insufficient thermal resistance and oil resistance (especially, anti-gasoline fume permeability).
Also, polyamide resin compositions comprising a polyamide resin and a thermoplastic polyurethane resin, which is blended therewith to reduce its tensile modulus, are known in the art. However, in general, the thermoplastic polyurethane resin constitutes a continuous phase in the polyamide resin composition when a relatively large amount of the polyurethane resin is blended for sufficient reduction of tensile modulus, and therefore provides some disadvantages due to the thermoplastic polyurethane resin. For example, the significant reduction of oil resistance (especially, anti-gasoline fume permeability), hydrolysis resistance, moldability (especially, mold releasing property), and the like can occur.